I would like to have a discussion on the evidences for common descent as presented in Douglas Theobald’s 29+ Evidences for Macroevolution on Talk.Origins. In particular, I would like to investigate whether each evidence (i.e., confirmed prediction) is not equally an evidence for common design. I propose to treat the evidences one by one in the order they are presented.

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1.1 The Fundamental Unity of Life. According to the theory of common descent, modern living organisms, with all their incredible differences, are the progeny of one single species in the distant past. In spite of the extensive variation of form and function among organisms, several fundamental criteria characterize all life. Some of the macroscopic properties that characterize all of life are (1) replication, (2) heritability (characteristics of descendents are correlated with those of ancestors), (3) catalysis, and (4) energy utilization (metabolism). At a very minimum, these four functions are required to generate a physical historical process that can be described by a phylogenetic tree.

If every living species descended from an original species that had these four obligate functions, then all living species today should necessarily have these functions (a somewhat trivial conclusion). Most importantly, however, all modern species should have inherited the structures that perform these functions. Thus, a basic prediction of the genealogical relatedness of all life, combined with the constraint of gradualism, is that organisms should be very similar in the particular mechanisms and structures that execute these four basic life processes.

That is, common descent predicts that all organisms are similar with respect to basic function and structure. And as function follows from structure, the prediction primarily concerns the basic structural similarity of all organisms.

It seems to me that similarity of structure is equally a prediction of common design. Consider the works of a common artist (e.g., paintings). It is a reasonable prediction that these works will share a basic structural similarity that differentiates them from works by other artists. Accordingly, an expert will be able to distinguish works by the one from those of others.

These are preliminary remarks, but should be enough to start discussion.

I sense a huge waste of time coming on here. Is there any circumstance possible that a sufficiently powerful and capricious designer does *not* explain? If not, of what possible use is an extended examination of the evidence to anyone who believes that a sufficiently powerful and capricious "designer" (nudge, nudge, wink, wink) did it? The evidence will never have the slightest effect on such a belief.

The point of Douglas Theobald's essay isn't that the evidence excludes a sufficiently powerful and capricious designer who, apparently, made things look exactly like the result of common ancestry. It's that the expectations of macroevolution and common descent match the available evidence.

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I'd like to make an observation on "intelligent design" in general. ID claims are aimed at obtaining a concession that evolutionary processes are insufficient to account for observed biological phenomena. After that, ID advocates hope that people will simply fill in with an "intelligent designer" of their preference to cover the gap. ID arguments are all of the negative variety: because evolution can't do this, you must accept that an "intelligent designer" did.

So, how do ID advocates wend their way toward finding evolutionary insufficiency? Do they identify phenomena with good evidential records of their origin and find that no natural mechanisms are able to cover the situation? No, they do not. ID advocates identify the systems that have the least evidence that can bear upon just how they might have arisen and whack on those. If evolutionary biologists don't have the evidence to work with, they certainly can't generate "detailed, testable pathways" that ID advocates like Rob claim it is their burden to produce. This is such a weak and pathetic strategy that the term I use for Michael Behe's arguments now is "God of the crevices". You see, Behe's claim to fame is to have taken the old young-earth creationist bleat of "what good is half a wing?" and bring it into the modern era of molecular biology, reborn as, "what good is half a flagellum?" Biochemistry, Behe says, is the basement floor, and there is no further place to go. Thus, the gaps Behe goes on about have a bottom, and are crevices.

Back in 2001, I was in a panel with William Dembski, and pointed out that the only way for ID to progress was to take up those case where there was evidence at hand. Things like the impedance-matching system of the mammalian middle ear and the Krebs citric acid cycle. Michael Behe was sitting in the audience at the time. Have ID advocates taken up those sort of systems for analysis? Not on your life.

"Intelligent design" advocates use Behe's "irreducible complexity" and Dembski's "specified complexity" as arguments to convince people to disregard theories which have some evidential support, and force acceptance of conjectures with no evidential support. It's a good trick, that.

Without some constraint upon the "designer" that supposedly is behind "common design", I don't see any sensible way to derive "predictions" from the concept. So I reject the notion that "similarities are a prediction of common design" until we've got some agreement on a set of constraints and purposes behind the "designer". Without that, all that can possibly come of it are "predictions" that are simply ad hoc inventions that have no contact with anything that we could call real.

I would add that in even this case a designer would have had the option of producing completely unrelated "designs" or those that embodied a radically new design element to implement one or more of these functions. With the diversity of life it has to be considered surprising that we do not see more variation in these areas - if common design were true.

Common design is less constrained than common descent and for that reason even if the intent were to compare the two hypotheses the evidence discussed would still favour common descent.

If the end result is some measure of clarity, even if only for myself, then I would not count the time wasted. And given your concern, I appreciate your reply.

The unity of life is an evidence for (i.e., confirmed prediction of) common descent. Is it equally an evidence for common design?

To this question you object:

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Without some constraint upon the "designer" that supposedly is behind "common design," I don't see any sensible way to derive "predictions" from the concept.

Let's return to the example of the artist. I stated that "It is a reasonable prediction that works [by a common artist] will share a basic structural similarity that differentiates them from works by other artists." Do you disagree? If so, on what basis does the expert attribute works to artists (cf. handwriting experts, philologists, etc.)?

I do not deny that an artist could, for whatever reason, produce radically dissimilar works, but that would be abnormal in some objective sense of abnormal, i.e., it is usually the case that works by the same artist are similar. Otherwise, the notion of a work being characteristic of an artist would be incoherent, and it clearly is not.

I would say that the elements under discussion represent engineering solutions more than artistic style and so the comparison is not very appropriate. How could we decide that these particular elements were stylistic rather than purely functional ?

Even if we were to consider the designer a pure artist, pure artists can and do work in different media requiring different techniques. So why not a different form of life embodying different mechanisms for one or more of the elements under discussion ?

So I don't see how we could make a strong prediction from a design perspective that any of these elements would be largely constant - let alone all of them.

My take on that is that different forms wouldn't have to be "radically dissimilar" in order to be enough different to conflict with what one would expect from descent from common ancestry.

Agreed; though counterfactuals are not relevant to my question. I am assuming that the actual unity of life is an evidence for common descent, and asking whether it is not equally an evidence for common design. Or more generally, are the evidences for common descent and common design coextensive?

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I also think the artist analogy is too loose to consider an inference from it to be reliable.

Perhaps it is, but it articulates an intuition everyone shares, viz., that the products of a person are more similar to each other than to the products of another. I think that intuition is correct, and am attempting to "tighten it up."

I would say that the elements under discussion represent engineering solutions more than artistic style and so the comparison is not very appropriate. How could we decide that these particular elements were stylistic rather than purely functional?

For the purposes of my question, the distinction between art and engineering is not relevant. If we use the broader sense of "art," every product of design is an artefact, e.g., a painting and a jet engine are both artefacts. Accordingly, the products of a single engineer will be more similar to each other than to those of another.

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Even if we were to consider the designer a pure artist, pure artists can and do work in different media requiring different techniques. So why not a different form of life embodying different mechanisms for one or more of the elements under discussion?

It seems to me that two basically different mechanisms (i.e., structures) performing the same function (e.g., replication) is not analogous to different techniques in different media (e.g., brush and paint, hammer and chisel).

No, I think that we do have to consider thaty the actual observed unity is one of solutions and that it is not clearly an aesthetic preference. THe Common Descent explanation expects these elements to be highly conserved, the Common Designer explanation has no basis for choosing these elements over any others. Nor is there such strong grounds for expecting a single unvarying "style" over such a wide range of - supposed - designs.

So in this instance Comon Descent is the superior explanation because it is more constrained in what it could potentially do.

No, I think that we do have to consider that the actual observed unity is one of solutions and that it is not clearly an aesthetic preference.

The unity is a unity of structure, and does not concern aesthetic preferences. I am employing a basic metaphysical principle, viz., that sameness of cause produces sameness of effect. That principle is operative in common descent and common design.

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The Common Descent explanation expects these elements to be highly conserved....

Conservation, here, is merely a reformulation of the metaphysical principle mentioned above. As such, it is proper to common design as well.

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...the Common Designer explanation has no basis for choosing these elements over any others.

That is a different issue. Whatever the elements (i.e., structures) are, common design predicts that they will be common. That is, the same elements will be shared by all organisms.

Would evidence for common descent look the same as separate creation by a common designer?

I don't think so. There might be commonalities of "style" from a common designer, but why would these quantitatively (as in DNA homology, for instance) track the geneologies of the creatures? If the same designer is responsible for starfish, chimps and humans, what - in the common designer argument - predicts any closer DNA relationship between any two of them compared with the third?

Okay, let's run with the artist and common design idea. Sorry for the size, but here are four images. Which of them have a common creator?An art historian could tell you that they are all Picasso, but the untrained eye would unlikely see the common creator.In contrast:andshow many similarities (music, abstract figures, domination by geometric shapes) but are done by different individuals (Miro and Picasso).Common design is not obvious.Especially in the case of God where we have no idea how he creates.

If you were simply referring to "similar causes produce similar effects" then the choice of an artist is an odd one. Naturally the "similar" elements produced by an artist would tend to be stylistic and thus we would expect aesthetic commonalities rather than functional ones.

Artists of all people would be the ones who most greatly undermine the simplistic use of the metaphysical principle you refer to, to apply to the output of intelligent designers.

But what amazes me most is the fact that you consider the fact that Common Descent provides strong grounds for these partiocular elements to be conserved to be a seperate issue from the fact that the Common Design does not. But this comparison is a clear indication that Common Descent is the better explanation for the conservation of these features. It is only by comparisons like this that we can determine which explanation is the better.

But most amazing of all is the final sentence which indicates that Common Design offers a tautology in place of explanation.

There are valid responses you could have offered - for instance an explanation of why Common Design WOULD predict that these particular elements would be conserved. You could have looked for other common elements that better fitted the Common Design argument. BUt you cannot claim that a prediction that maybe some elements will be common to all life is as good as a prediction that specific elements are very likely to be common to all life.

Let's return to the example of the artist. I stated that "It is a reasonable prediction that works [by a common artist] will share a basic structural similarity that differentiates them from works by other artists." Do you disagree? If so, on what basis does the expert attribute works to artists (cf. handwriting experts, philologists, etc.)?

On the argument to rarefied design inferences from ordinary design inferences: This ground has been covered. John Wilkins and I have been there and done that.

Basically, I'm pointing out that the claimed analogy between known designers with whom we have experience and unknown designers operating in unknown ways is illegitimate. So, yeah, I dispute Michael's claim above as having any bearing upon my original objection. There is no basis given by Michael (or anyone else from Paley right on down to today) for a claim of "prediction" of what a designer behind aspects of life must have done.

Paul Nelson argued in 1997 that the argument from suboptimality as an impeachment of design was flawed because the argument depended upon theological themata: what was "disproved" by such arguments was not design per se but rather a particular theological theme concerning a putative designer. There were problems in Nelson's argument concerning whether a principled suboptimality argument was possible (I showed that one could easily construct a relative figure of merit that did not depend upon unobservable values), but the basic insight that to make claims about such a designer is to deal in theological themes seems good to me. And the issue cuts both ways. While arguments against theological themes don't eliminate design per se, neither do theological themes provide any basis for claims of "predictions" of design, either.

Michael's conjectures about design outcomes are, at basis, dabblings in theology. They don't tell us anything about what to expect in the empirical evidence.

(1) Argue that the predictions of common descent and common design are coextensive.

(2) Argue that the “predictions” of common descent are not predictions, but are merely consistent with common descent.

(3) Use an inductive elimination (i.e., a destructive dilemma with an inductive disjunction) to argue against the viability of the mechanism(s) of common descent.

(1) is out because nobody has figured out how to make predictions from "common design".

(2) is out because it is a distinction without a difference. F'rinstance, the genetic codes of living organisms on earth are largely shared, giving the "canonical genetic code" that the vast majority of organisms use. In the cases where organisms use an alternative code, the differences also show a pattern of descent with modification. But that is not the way things had to be. There are many possible alternative genetic codes. Not only are there enough alternative possibilities to give every species that has ever existed its own code, but every single individual that has ever lived could have been given its own unique genetic code. If we observed such a state of affairs, we would not be trying to explain it via common descent. It is clear that empirical evidence could disallow common descent. Whether one chooses to use "prediction" or "consistency with the available evidence" is pure semantics. There are possible states of the evidence that common descent would not be able to accommodate. Douglas Theobald's FAQ goes over many of them.

(3) is intellectually dubious. It is, precisely as stated by Lenny Flank on PT, the "god of the gaps" argument.

It seems to me that Lenny did concisely point out the fundamental errors in Michael's argument. The fact that Lenny is abrupt to the point of rudeness does not set aside the observation that he is also correct.

I'm not aware of any tenet of ID that says there can only be ONE designer, although that seems to be the presumption. Thus if several or a million designers were operating throughout history, radically different designs would be possible or even likely. Therefore the absence of common design in no way disproves ID. The presence of features usually accepted as supporting common descent is pretty weak evidence FOR ID. And, as noted, absence of common design doesn't count against ID, unless you argue there can only be one designer, and that comes perilously close to giving the Designer a name...

The issues I brought up are general issues, not specific to discussion of "the unity of life". They aren't going to go away or change because you start a new thread.

I will be happy to repost these criticisms to whatever new thread carries on, if no change in the mode of argument occurs. One would hope that there would be some notice taken of the critiques, but I've been doing this far to long to hold out much hope for that.

I have conceded defeat on "the unity of life" prediction. Perhaps we can discuss nested hierarchies in turn.

So long as the designers intentions and capabilities are left undefined there is no good way to say what the designer would produce.

The best you can hope for is that in some cases a designer might produce the same result as common descent - but always the prediction would be weaker, since there is no way to say that the designer WOULD produce that result rather thna some other.

Your strategy - which I grant is the preferred strategy for ID - essentially prevents you from being able to produce positive arguments for design. If you are serious about exploring a design explanation then you badly need to produce a far more concrete idea of the designer.

I did not mean to imply that I would go about a discussion of nested hierarchies in the same way. As no predictions follow from a designer, no predictions about nested hierarchies follow from a designer. Thus, the conclusion I reached concerning the unity of life can be generalized to cover the other predictions of common descent.

I wanted to discuss this statement of yours:

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(2) is out because it is a distinction without a difference. ...Whether one chooses to use "prediction" or "consistency with the available evidence" is pure semantics. There are possible states of the evidence that common descent would not be able to accommodate.

I think the distinction presents a difference. Common descent is the theoretical claim (sentence) that "all known biota are descended from a single common ancestor." A prediction of common descent is an observation claim (cf. Quine's observation sentence) that is logically deduced from the theoretical claim, e.g., "cladistic analyses of organisms produce phylogenies that have large, statistically significant values of hierarchical structure."

A prediction is a logical implication of the theoretical claim. Accordingly, the theory can be falsified using a modus tollens:

On the other hand, an observation claim is merely consistent with a theoretical claim if both can be true together, but the falsity of the observation claim does not imply the falsity of the theoretical claim. Statements that are merely consistent with a theoretical claim cannot be deduced from that theoretical claim. For example, observation claims concerning the unity of life are consistent with my previous theoretical claim that "all known biota are special creations of a single designer," i.e., they can both be true together, but the latter does not follow logically from the former, and its falsity does not result in the falsity of the thoeretical claim.

My question, then, is whether the observation claim that "cladistic analyses of organisms produce phylogenies that have large, statistically significant values of hierarchical structure" is a prediction of common descent or whether it is merely consistent with common descent? Is there a conceivable scenario in which common descent would be true and the observation claim false? If there were, the observation claim could not be a deduction from from the theoretical claim, and therefore, it could not be a prediction.

That's folderol, Michael. "Logically produced" statements include both universal statements (to which one can then apply modus tollens to, as Popper famously noted) and existential statements (to which one cannot apply modus tollens). So even by Michael's connotation of "prediction" as a "logically produced statement", he hasn't constrained the output to the desired class of universal statements.

There is a term in logic for strict logical implication. Let's see how long it takes for Michael to comes up with it.

Then, Michael can go back to the statement by Theobald at the start of this thread and try to apply his distinction there. To me, it sure looks like that would put the theory at risk if it were found to be false. Which, I will remind Michael, was already noted by me in my statement, and which he failed to address:

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There are possible states of the evidence that common descent would not be able to accommodate.

Guess its back to the drawing board for the pseudoscience crowd regarding humans and chimps common ancestor.

I'm sure another fairy tale will quickly take the old one's place.. they always do.

Really? In that case, I look forward to the Flying Spaghetti Monster replacing creationi.....ID. It has as much evidence as ID, after all.

--------------Fundamentalism in a nutshell:"There are a lot of things I have concluded to be wrong, without studying them in-depth. Evolution is one of them. The fact that I don't know that much about it does not bother me in the least."

I see the intellectual content of your replies is up to evolutionist standards...totally void.

Of course my entry referred to and quoted an article in a peer reviewed journal announcing the discovery and its implications for the formerly held explanations of the divergence of chimps and human ancestors, etc. namely the former explanation was ruled out and an entire new explanation has to be developed. As usual the overturning of evolutionary explanations by messy facts in no way diminishes the theory since it can accommodate any occurrence or finding imaginable being completely plastic, having no quantitiative aspects of consequence and being founded upon sky hooks hanging upon nothing.

If one accepts that the universe, solar system, earth itself, its atmosphere, biosphere, chemical makeup etc. preceeded life and I think there is common agreement on that premise; then what life forms could be created except those who had to successfully inhabit a world with an atmosphere and food source common to them all in large part and governed by the same physical laws of gravity, thermodynamics, chemistry, atomic theory etc.

Thus within limited variation a purposeful designer would by necessity and as a consequence of prior creative choices preceeding life have to have common design elements for respiration, energy conversion, metabolism, waste elimination, sensory perception, movement and motion in a gravitational field.

The only other boundaries on such a designer would be his own character and sovereign intentions, that would be sufficient.

Of course one can choose the ultimate in inefficiency, the most unintelligent approach to design ,, but that would be evolution by random mutation and natural selection.

Clearly no one serious about accomplishment in finite time and finite cost ever chose that method.. it simply could never create anything of any modest complexity... we can be sure of that by our use of mathmatical statistics and many have done so.

peach: Your month old article you just found at some ID bloggers site, well on the same site they have this: New findings boltster case for ancient human ancestor I guess it is like the typical creationist to trumpet victory before any science has been done. Its funny how when dealing with teeth, they aren't good enough for any argument supporting evolution, but all it takes is a few teeth for this IDC parrot to jump around in jubilation at the defeat of the evil darwinists.

I see the intellectual content of your replies is up to evolutionist standards...totally void.

Well, you know what they say: If you can't beat them (fundies, by using your God-given brain), join em (by removing every trace of rationality and logic). So I thought I'd play at being a fundie tonight.

--------------Fundamentalism in a nutshell:"There are a lot of things I have concluded to be wrong, without studying them in-depth. Evolution is one of them. The fact that I don't know that much about it does not bother me in the least."

As usual your nonsensical, vacuous responses contain no chain of logic, no critical thinking elements just blather and invective.

I printed off your last half dozen posts and had the prof who teaches Elements of Critical Thinking at our college read them in context.

He just chuckled and said you two people were just untrained and largely uninformed zealots and I was probably wasting my time trying to discuss things requiring considerable intellect.

I guess I should allow you the opportunity to prove him wrong, so do you have anything with intellectual content to say that supports your theory.

In passing, the article on the huge problem for common decent between chimps and people was taken directly from the various peer reviewed journal abstracts I subscribe to and only published in the last ten days.

Now if you care to address the prior post on common design elements in a logical fashion or better the helium to brain issue ... well its your chance boys .. prove my prof wrong.